1. Field of the Invention
The present invention relates generally to a Cognitive Radio (CR)-based wireless communication system, and in particular, to an apparatus and method for detecting a Television (TV) signal on a radio channel.
2. Description of the Related Art
Along with the rapid development of wireless communication systems and a variety of wireless communication services, strict frequency separation is required for communication systems to coexist. Yet, there is only a limited spectrum available due to multiple applications over all of frequencies which can be commercially used. Hence, deployment of a new wireless platform faces a serious shortage of spectrum resources, particularly in lower frequency bands than a few gigahertz. To solve this spectrum shortage, the concept of CR has been introduced, which is a technique for detecting allocated but unused spectrum and efficiently sharing the unused spectrum.
Many countries have strictly regulated the use of frequency resources subject to their frequency policies, and service providers use frequencies through licensing and allocation from their governments. The CR technology enables the use of allocated but unused frequency resources.
In order to meet the recent increasing demand for the limited frequency resources, there is a pressing need for the CR technology, which has attracted much interest since the US Federal Communications Commission (FCC) commented on the possibility of frequency sharing in a Notice of Proposed Rule Making (NPRM) in December, 2003. Such a major example is a standardization of the Institute of Electrical and Electronics Engineers (IEEE) 802.22 Wireless Regional Area Network (WRAN) seeking the development of a CR-based communication platform. The IEEE 802.22 WRAN system is expected to be deployed in suburban areas of the U.S. or Canada, or in developing countries, aiming to provide wireless communication services using the CR technology in an unused TV frequency band.
CR standardization and development is active but in an early stage. Hence, there exist many issues to be handled and most of the configurations for the CR technology are yet to be specified.
CR, a technology for radio channel management, distribution, and interference detection using multiple channels, has a potential for interworking with future-generation wireless communications in a complementary fashion. For example, the CR technology can enable effective high-speed data transmission without frequency interference in shadowing areas existing under a cellular environment or in suburban areas requiring an increased cell size.
However, there are challenging issues to tackle in the application of CR to actual wireless communication systems. A major example is to detect a TV signal (hereinafter, simply referred to as a signal) to search for an unused channel.
In conventional signal detection, the power of a frequency band is measured. After the power measuring, the power measurement is compared with a predetermined threshold. For example, if the power measurement is equal to or less than the threshold, it is determined that no signal is detected. If the power measurement is greater than the threshold, it is determined that a signal exists in the frequency band and the signal is detected.
However, the conventional signal detection method cannot ensure reliability and suffers performance degradation.